Multi-region imaging systems

ABSTRACT

An imaging system includes optics for forming an optical image, that provide a first region in the optical image that is characterized by a first range of best focus and a second region in the optical image that is characterized by a second range of best focus The first and second ranges correspond to object distance ranges that are discontiguous A sensor array converts the optical image to a data stream, and a digital signal processor processes the data stream to generate a final image.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional patent applicationSer. No. 60/953,998, filed Aug. 4, 2007, entitled MULTI-REGION IMAGINGSYSTEMS AND ASSOCIATED METHODS, and to U.S. Provisional patentapplication Ser. No. 61/056,730, filed May 28, 2008, MULTI-REGIONIMAGING SYSTEMS. All of the above-identified patent applications areincorporated by reference in their entireties.

BACKGROUND

Traditional imaging systems are commonly designed so that the finalimage quality is high over a narrow region of object space; for example,objects located over a narrow range of object conjugate distances may beimaged by the traditional imaging system to form an in-focus image. Thedepth of this narrow region of the object space is determined by thedepth of field of the system. More recent imaging systems may employnon-traditional imaging designs and techniques that allow an increaseddepth of field compared to classical systems. For example, U.S. Pat. No.5,746,371, entitled EXTENDED DEPTH OF FIELD OPTICAL SYSTEMS issued 5 May1998, discloses imaging systems configured to provide an increased depthof field.

SUMMARY OF THE INVENTION

An imaging system includes optics for forming an optical image thatprovide a first region in the optical image that is characterized by afirst range of best focus and a second region in the optical image thatis characterized by a second range of best focus. The first and secondranges correspond to object distance ranges that are discontiguous. Asensor array converts the optical image to a data stream, and a digitalsignal processor processes the data stream to generate a final image.

In an imaging system including imaging optics and a sensor array, animprovement includes an optical element within the imaging system andintersecting at least a portion of electromagnetic energy incident onthe sensor array. The optical element cooperates with the imaging opticsand the sensor array to form a first image portion and a second imageportion from the electromagnetic energy. The first image portion is infocus over a first conjugate distance range and the second image portionbeing in focus over a second conjugate distance range. The two conjugatedistance ranges are separated by at least 40 cm.

In a method of imaging utilizing imaging optics and a sensor array, animprovement includes configuring the imaging optics such thatelectromagnetic energy transmitted through the imaging optics andincident on the sensor array forms an image that is in focus over atleast two conjugate distance ranges for two respective portions of theimage. The two conjugate distance ranges are separated by at least 40cm.

BRIEF DESCRIPTION OF DRAWINGS

The present disclosure may be understood by reference to the followingdetailed description taken in conjunction with the drawings brieflydescribed below. It is noted that, for purposes of illustrative clarity,certain elements in the drawings may not be drawn to scale.

FIGS. 1 and 2 show possible application scenarios suitable for use witha multi-region imaging system, in accordance with an embodiment.

FIG. 3 shows a block diagram of a multi-region imaging system, inaccordance with an embodiment.

FIGS. 4-7 illustrate an analysis and design approach for configuring amulti-region imaging system, in accordance with an embodiment.

FIG. 8 shows a plot of an exemplary one dimensional exit pupil phaseprofile, in accordance with an embodiment.

FIG. 9 shows a plot of an ambiguity function for a diffraction-limitedimaging system.

FIGS. 10 and 11 show plots of ambiguity functions for a cubic phaseimaging system and a multi-region imaging system, respectively, inaccordance with an embodiment.

FIG. 12 shows a block diagram of an exemplary imaging system, inaccordance with an embodiment.

FIG. 13 shows a plot of a through-focus MTF curve for the exemplaryimaging system of FIG. 12 without a specialized phase surface.

FIG. 14 shows a surface sag plot of one example of design of an asphericsurface of the imaging system of FIG. 12, in accordance with anembodiment.

FIG. 15 shows a plot of a through-focus MTF curve for the exemplaryimaging system of FIG. 12, this time including the aspheric surfacespecified in FIG. 14, in accordance with an embodiment.

FIGS. 16-19 show polychromatic MTF curves for the system of FIG. 12including the aspheric surface of FIG. 14 at different conjugatedistances, in accordance with an embodiment.

FIGS. 20-24 include polychromatic MTF curves of the same system as thoserelated to FIGS. 16-19, but which has been optimized to also provideadequate imaging at 25 cm conjugate distance, in accordance with anembodiment.

FIG. 25 illustrates another example of an aspheric surface suitable foruse in the system of FIG. 12, in accordance with an embodiment.

FIG. 26 shows the through-focus MTF for an imaging system of FIG. 12modified to utilize the surface of FIG. 25, in accordance with anembodiment.

FIGS. 27-30 show polychromatic MTF curves related to the system of FIG.12 utilizing the surface of FIG. 25, in accordance with an embodiment.

FIG. 31 shows another example of a multi-region imaging system, inaccordance with an embodiment.

FIG. 32 shows a plot of the polychromatic through-focus MTF curve of thesystem designed in accordance with TABLES 6 and 7, in accordance with anembodiment.

FIGS. 33-35 show monochromatic through-focus MTF curves of the systemdesigned in accordance with TABLES 6 and 7, in accordance with anembodiment.

FIGS. 36-39 show polychromatic MTF curves at various conjugate distancesfor the system designed in accordance with TABLES 6 and 7, in accordancewith an embodiment.

FIG. 40 shows a block diagram of a multi-region imaging system includingsub-wavelength features, in accordance with an embodiment.

FIG. 41 shows an example of a sub-wavelength feature profile suitablefor use with a multi-region imaging system, in accordance with anembodiment.

FIG. 42 shows an ambiguity function related to the combination of adiffraction-limited imaging system and the sub-wavelength features ofFIG. 41, in accordance with an embodiment.

FIG. 43 shows a surface sag according to the prescription summarized inTABLE 8, in accordance with an embodiment.

FIG. 44 shows a polychromatic through-focus MTF for a system includingthe surface of FIG. 43.

FIGS. 45-48 show the MTF curves at a variety of object distances for themulti-region imaging system including the surface sag of FIG. 43, inaccordance with an embodiment.

FIG. 49 shows the perspective of a forward-looking imaging system asseen from the inside of an automobile, in a similar scenario asdescribed in FIG. 2, in accordance with an embodiment.

FIG. 50 shows a block diagram of a spatially varying multi-regionimaging system, in accordance with an embodiment.

FIG. 51 shows a block diagram of an exemplary spatially-varyingmulti-region imaging system, in accordance with an embodiment.

FIGS. 52-55 show the polychromatic diffraction MTF curves for thespatially-varying multi-region imaging system of FIG. 51, in accordancewith an embodiment.

FIG. 56 shows the through-focus MTF curves for the spatially-varyingmulti-region imaging system of FIG. 51, in accordance with anembodiment.

FIGS. 57-62 illustrate different aperture configurations for themulti-region imaging system of FIG. 51.

FIGS. 63-75 illustrate a variety of different assembly configurationsfor the multi-region imaging system of FIG. 51.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

While the depth of field of an imaging system may be increased usingdifferent techniques, certain limitations may exist. For example, theheight of a modulation transfer function (“MTF”) at a particular spatialfrequency over a range of conjugate distances (also known as a“through-focus MTF”) is a quantity related to image quality achievableby an imaging system. (Note, throughout this application the term“conjugate distance” is meant in the sense of object conjugatedistance.) For a given application, a designer of the imaging system maynot arbitrarily set the height of the through-focus MTF, since a maximumvalue of the MTF at a particular conjugate distance is determined by adiffraction-limited MTF. While the through-focus MTF curve for atraditional imaging system generally includes one peak at a particularconjugate distance and drops to nearly zero away from the peak, thethrough-focus MTF curve for an extended depth of field imaging systemsmay have a non-zero value over a range of conjugate distances. Inextended depth of field imaging systems, the height of through-focus MTF(and/or light gathering ability of the imaging system) may also droprelative to that of the diffraction-limited system.

A mathematical approach to understanding the aforementionedthrough-focus MTF drop with increased depth of field is to consider ageneral monochromatic exit pupil phase function P(x) for a givenaperture, where:|P(x)|=1 within the aperture,  Eq. (1)andP(x)=0  Eq. (2)outside of the aperture.

The through-focus MTF for a particular spatial frequency may be given bythe equation:Through−focus MTF(ω)=|Fourier Transform(P(x−a)P(x+a)*)|,  Eq. (3)where a is a constant related to the particular spatial frequency ωand * denotes complex conjugate. From Parseval's theorem, it is knownthat the sum of the squared magnitude of two signals related by FourierTransform are equal. In other words, for a particular spatial frequencyω, the sum of the squared through-focus MTF values is equal for allimaging systems that meet the definitions above. Consequently,ΣThrough−focus MTF(ω)²=constant  Eq. (4)for all P(x).

The consequence of the above mathematical description is that the heightof the through-focus MTF over a range in object or image space (e.g.,over a range of conjugate distances) is limited. That is, increasing arange of clear imaging in object space leads to a reduction in height ofthe MTF. This same concept, in the context of an ambiguity function, isalso called “conservation of ambiguity”.

In order to overcome the aforedescribed limitations and to meet theneeds of advanced applications, various embodiments of multi-regionimaging systems are disclosed herein. In accordance with an embodiment,a multi-region imaging system is a single aperture imaging system thatis configured for providing good imaging performance at two or morespatial regions (e.g., in conjugate distance, image region or both) in asingle exposure. The multi-region imaging system may be implemented ashaving, for instance, a monochromatic exit pupil, a polychromatic exitpupil, a polarization-dependent exit pupil or polarization-dependentimage plane, or a combination thereof. The multi-region imaging systemmay also be connected with a processor for performing one or more offorming a human viewable image, transmitting captured image data toanother location, and processing the captured image data to perform atask. Such processor may utilize information of optics forming the twoor more spatial regions to process each region so as to provide a clearimage of each region.

There are various applications of imaging systems where good low lightperformance and clear imaging over a large range of object distances aredesired. One example is shown in FIG. 1, which illustrates desiredimaging characteristics for a mobile phone camera. FIG. 1 shows ascenario 10, in which a mobile phone camera 20 may be required toprovide good performance in near field imaging, such as imaging abarcode 30, as well as far field imaging, such as imaging a portraitsubject 40 at a distance of ½ meter or more. That is, it would bedesirable to obtain sharp imaging of objects from infinity to portraitdistance as well as very close imaging, on the order of 10 to 12 cm fromthe camera, for reading and decoding near objects such as barcodes andbusiness cards. Additionally, good low light imaging performance in sucha mobile phone camera may be achieved by using fast lenses (e.g.,≦F/2.0). The use of fast lenses generally translates to decreased depthof field and increased close focus distance with clear infinity imaging.Specifically, increasing the speed of the lenses to F/2 and faster mayeither move the close focus conjugate distance far from the close focusdesired distance, or unacceptably decrease the image quality. Theembodiments herein help alleviate such reductions in image quality andother problems.

Another example of an application requiring good low light performanceand clear imaging over a large range of object distances is inautomotive imaging systems, such as illustrated in FIG. 2. FIG. 2 showsa scenario 50, in which an automobile 60 approaches a street sign 70.Automobile 60 may include a camera 75 for capturing images of objectsoutside of the automobile. Camera 75 may be used in forward lookingimaging systems for object recognition, for example, to recognize streetsigns, pedestrians and lane demarcation lines. Camera 75 may be furtherconnected with a processor 80, which may perform functions such asobject recognition on images captured by camera 75. While ahuman-viewable image is not always necessary for object recognition,capturing information may be desirable at times for objects far fromcamera 75 (e.g., objects located at infinity) for use in, for instance,a task-based image capture and processing application. Additionally, itmay be desirable in some situations for the imaging system to be capableof directly imaging at near field distances, such as a windshield 85 ofautomobile 60; for instance, near field imaging may be integrated intoactivation of rain sensors and/or to warn a driver when windshield 85 isdirty. Processor 80 may be further connected with a central computer 90of automobile 60 so as to effect certain actions by automobile 60 inreaction to detected triggers, such as activation of windshield wipersin the case of rain. Due to automobile design constraints, the distancefrom camera 75 to windshield 85 may be as little as 5 cm in someautomobiles. As in the mobile phone application of FIG. 1, the use offast lenses in camera 75 may improve low light performance, although theclose focus conjugate distance may be increased as a result.

An exemplary block diagram of an exemplary multi-region imaging systemis shown in FIG. 3. A multi-region imaging system 300 includesmulti-region optics 310, a sensor 320 and a processor 325. Multi-regionoptics 310 may include, for example, specialized optics for imaging botha near object 330 and a far object 335 in one image onto sensor 325.Sensor 320 captures the image so as to generate image data 315 inaccordance with the captured image. Processor 325 may implement imagesignal processing (“ISP”) to act on image data 315, for instance, toproduce a human-viewable image 340 or a processed result 345 related toa task, such as reading and decoding a barcode, business card or streetsign. Processor 325 may utilize information of multi-region optics 310to optimize processing of each region to produce a clear image for eachregion. Optionally, multi-region imaging system 300 may be configured tosimultaneously produce both human-viewable image 340 and task-relatedresult 345, as will be further described hereinafter.

The operational concepts behind the multi-region imaging system, such asmulti-region imaging system 300, are described in conjunction with FIGS.4-12. For simplicity, one-dimensional optics are considered in thesefigures, assuming incidence of parallel light rays from infinity on oneside of each lens (from the left side of each figure). Consider theray-based drawings of a traditional imaging system 400 of FIG. 4 and anextended depth of field (“EDoF”) imaging system 500 as shown in FIG. 5.Traditional imaging system 400 includes optics 410 with an optic axis412 configured for focusing incident rays 415, from the left hand sideof FIG. 4, at a plane of best focus 420, which is indicated in FIG. 4 asa dot-dash line to the left of optics 410. Traditional imaging system400 has essentially one plane of best focus; that is, parallel rays 415through all portions of optics 410 generally come to a focus at the sameplane 420. In contrast, EDoF imaging system 500 includes a combinationof optics 410 with a phase modifying element 510; one suitable exampleof phase modifying element 510 is a phase mask, such as that describedin U.S. Pat. No. 5,748,371 by Cathey, et al., entitled “Extended depthof field optical systems” (hereinafter, “the '371 patent”). Thecombination of optics 410 and phase modifying element 510 is configuredsuch that incident rays 415 are imaged to an extended imaging region 520(as indicated by a bracket) over a range of image distances or, in otherwords, planes of best focus. The planes of best focus may be contiguoussuch that the depth of field provided by EDoF imaging system 500 isextended over a range of imaging or conjugate distances, therebyresulting in an extended depth of field imaging system.

For example, for an extended depth of field imaging system including acubic phase function for modifying the wavefront of electromagneticenergy transmitted therethrough (such as that described in the '371patent), the monochromatic exit pupil phase function of the resultingimaging system is given by a one-dimensional phase function P(x) as afunction of x:P(x)=exp(jαx ³)  Eq. (5)within the aperture, where α is a constant and j=√{square root over(−1)}, andP(x)=0  Eq. (6)outside of the aperture. That is, the phase modification imposed on thewavefront of incident rays 415 by the combination of optics 410 andphase modifying element 510 in this case is αx³. The second derivativeof this phase modification is an expression approximating the focallength across the exit pupil as a function of position:Focal Length≈α*6x.  Eq. (7)

In other words, the cubic phase modification provided by the presence ofphase modifying element 510 in EDoF imaging system 500 results in anapproximately linear focal length change across the exit pupil.

One way to consider the effects of phase modifying element 510 in EDoFimaging system 500 is to regard phase modifying element 510 as beingcomposed of a plurality of small optics segments, such as shown in FIG.6, with the focal lengths of these lenses linearly changing across theaperture in accordance with the expression α*6x as derived above. In theexample shown in FIG. 6, an EDoF imaging system 600 includes a phasemodifying element 610, which is formed from a plurality of opticssegments 612A-612F. The combination of phase modifying element 610 andoptics 410 provides a linearly changing focal length in accordance withthe expression α*6x, thereby providing the equivalent extended depth offield effect as that provided by the combination of phase modifyingelement 510 with optics 410, as shown in FIG. 5, assuming the number ofoptics segments 612 is large enough so that the height of each of thesteps among segments 612A-612F is, for example, on the order of awavelength or less. In other words, the combination of phase modifyingelement 610 and optics 410 images over an extended imaging region 620(as indicated by a bracket) over a range of imaging distances that isequivalent to extended imaging region 520 provided by the combination ofphase modifying element 510 and optics 410, as shown in FIG. 5.

While six optics segments 612A-612F are shown in FIG. 6, more or feweroptics segments may be used in a given EDoF imaging system. A designerof an EDoF imaging system may consider optics segments 612A-612F havingdimensions on the order of approximately a wavelength of incidentillumination of interest, such that a finite number of optics segmentswould be used in approximating the performance of EDoF imaging system600. In such a consideration, the EDoF imaging system may beconceptually regarded as partitioning incident rays with optics segments612A-612F, wherein each optics segment has a focal length thatapproximately focuses at a particular region along a range of imagingdistance. Having extended depth of field means that fewer opticssegments may be used to image any one point of an object. Conversely,having a reduced depth of field means that each point of the object isimaged using more of these optics segments. Another way to view thissituation is, as more of these optics segments are used to image eachpoint of a given object, then a height of a resulting through-focusmodulation transfer function (“MTF”) for these object points willincrease; on the other hand, as fewer optics segments are used to imageeach object point, the height of the resulting through-focus MTF forthese points will decrease. It should be noted that this description isa simplified, one-dimensional first order approximation of the presentsystem and should be considered illustrative only.

Rather than requiring imaging over a broad range of imaging distances,the multi-region imaging system may be configured to simultaneouslyimage objects located at specific, possibly non-adjacent regions in theobject space. For example, these non-adjacent regions may not becontiguous in object space. As a result, a multi-region imaging systemmay exhibit higher MTF heights and simpler configurations compared toprior imaging systems, as will be further discussed immediatelyhereinafter.

Consider the multi-region imaging system shown in FIG. 7. Instead ofrequiring that the combination of optics image objects along a broadrange of imaging distances, as shown in FIGS. 5 and 6, each portion ofthe imaging system aperture is used to image only a specific region inobject space. In the example shown in FIG. 7, a multi-region imagingsystem 700 includes a phase modifying element 710, including a pluralityof optics segments 712A-712D. Optics segments 712Λ and 712B areconfigured to cooperate with optics 410 so as to image in a near region720 (as indicated by a bracket) over a range of near imaging distances.Optics segments 712C and 712D are configured to cooperate with optics410 so as to image in a far region 725 (as indicated by another bracket)over a range of far imaging distances. Certain conjugate distances inobject space may fall into a “don't care” region 730 that does not needto be imaged. Due to the finite total MTF limitation described earlier,having distinct object regions and/or “don't care” regions allows higherthrough-focus MTF heights for those object regions of interest,specifically in near region 720 and far region 725. Viewed another way,multi-region imaging system 700 provides a single imaging system that isequivalent in performance to another system that uses distinct sets ofimaging optics for imaging over non-adjacent, narrow regions in objectspace. Like phase modifying element 610 (FIG. 6) being broken up intosix segments 621A-612F, phase modifying element 710 is shown as segments712A-712F for illustrative purposes only. That is, phase modifyingelement 710 may have other configurations, such as curved segments or acontinuous aspheric surface.

Still referring to FIG. 7, multi-region imaging system 700 is configuredsuch that the upper half of the aperture (i.e., optics segments 712A and712B) may be used to image one region in object space and the lower half(i.e., optics segments 712C and 712D) may be used to image anotherregion in object space. While optics segments 712A and 712B are shown asbeing split into the upper and lower halves of the aperture, it isrecognized herein that other configurations are also possible. Thecorresponding multi-region exit pupil phase may be expressed as:Phase multi-region(x)=αx ³+Lower(x)/βx ²,  Eq. (8)where the αx³ term corresponds to a cubic phase term. The term Lower(x)equals zero for the upper half of the aperture (i.e., optics segments712A and 712B), and unity for the lower half of the aperture (i.e.,optics segments 712C and 712D). The term βx² is a focusing or opticalpower term. The constants α and β may be specified by the designer for aspecific system. Comparing the above expression with the phase functionfor the cubic phase modification given by Eqs. (5) and (6), theexpression for multi-region phase contains an extra Lower(x)βx² term,which is specific to a particular section of the aperture.

FIG. 8 shows a plot 800 of an exemplary one dimensional exit pupil phaseprofile, in accordance with the above multi-region exit pupil phaseexpression of Eq. (8), with α=5 and β=40. The vertical axis representsaperture phase in radians, while the horizontal axis shows aperturedimension x in arbitrary units. As may be seen in FIG. 7, the aperturephase is zero or less for the upper half of the aperture (i.e., throughoptics segments 712A and 712B), while the lower half of the aperture(i.e., optics segments 712C and 712D) provides position-dependent phasemodification.

An ambiguity function (“AF”) plot 900 related to a diffraction-limitedimaging system, such as that exemplified by FIG. 4, is shown in FIG. 9.The horizontal axis (“u-axis”) in plot 900 represents spatial frequencyanalogous to the spatial frequency axis of an MTF plot. As is known inthe art of AF analysis, the vertical axis (“v-axis”) has no directrelationship to the physical imaging system, but the projection ofradial slices of the AF onto the horizontal axis may be interpreted asthe MTF of this imaging system for varying amounts of misfocus. As isknown in the art of AF analysis, darker shades in FIG. 9 representhigher MTF values. In other words, radial cross-sectional slices of theAF yield MTF curves for different values of misfocus and spatialfrequency. As is well known in the art, the AF represents a polardisplay of the MTF as a function of misfocus, and radial lines throughan origin 940 of AF plot 900 represent the MTF at varying degrees ofmisfocus. A radial line with zero slope (e.g., dotted line 910)corresponds to MTF at zero misfocus, radial lines with increasing slopes(e.g., dotted line 920) correspond to the MTF at increasing misfocus,and a vertical line (e.g., dotted line 930) through AF plot 900corresponds to the through-focus MTF at a particular spatial frequencyu. It may be noted that the diffraction-limited AF, as represented byplot 900, is narrow in the vertical direction, thereby indicating highsensitivity of the resulting MTF to misfocus; that is, away from thehorizontal radial line corresponding to a zero misfocus value (i.e.,dotted line 910), the MTF curves corresponding to AF plot 900 exhibitvery sharp peaks with low MTF values away from the sharp peaks, therebyindicating poor imaging quality outside of a very narrow conjugatedistance range.

FIGS. 10 and 11 show AF plots 1000 and 1100 for a cubic phase imagingsystem with α=10 (such as, for example, that shown in FIG. 4 and inaccordance with Eqs. (5) and (6)) and for a multi-region imaging systemwith α=5 and β=40 (e.g., that shown in FIG. 7 and in accordance with Eq.(8)), respectively. In FIG. 10, a slanted radial line 1020 correspondsto the MTF at non-zero misfocus for the cubic phase imaging system, anda vertical line 1030 corresponds to the through-focus MTF at aparticular spatial frequency. Similarly, in FIG. 11, a slanted radialline 1120 corresponds to the MTF at non-zero misfocus for themulti-region imaging system, and a vertical line 1130 corresponds to thethrough-focus MTF at a particular spatial frequency. It may be seenthat, in contrast to the diffraction limited imaging system AF plot ofFIG. 9, both the cubic phase imaging system and the multi-region imagingsystem exhibit ambiguity functions with broader dark regions in thevertical direction, corresponding to higher MTF values; that is, ratherthan a narrow dark line at the zero slope as in AF plot 900, AF plots1000 and 1100 include broader shaded sections in a horizontal bowtieshape, indicative of higher values over a broader MTF peak correspondingto AF plots 1000 and 1100. In other words, the AF plots of FIGS. 10 and11 indicate that these imaging systems exhibit good imaging quality evenwith non-zero misfocus values. It is known that an ambiguity functionrepresents optical MTF, and a system's sensor spatial frequency limit istypically half or less than the system's optical limit; the extent of atypical spatial frequency extent for a digital sensor is indicated bybrackets 1035 and 1135 in FIGS. 10 and 11, respectively. Furthermore, AFplot 1100 corresponding to the multi-region imaging system exhibits twoclear regions of best focus separated by a “don't care” region(indicated by two dashed ovals 1140A and 1140B).

A number of variations to the multi-region imaging system are possible.While the example illustrated in FIGS. 7 and 11 assumed a rectangularlyseparable exit pupil phase, other types of phase modification such as,but not limited to, circularly symmetric phase, symmetric phase ornon-symmetric exit pupil phase may also be used, according to a desiredapplication. The use of polychromatic (that is, wavelength-dependent)exit pupil phase design is also possible, and the phase modification maybe effected by, for instance, phase modulating optics withsub-wavelength features. Alternatively, the phase modification may beimplemented using polarization-dependent optical elements.

FIG. 12 shows a block diagram of an exemplary multi-region imagingsystem 1200. FIG. 12 is a particular example of the general multi-regionimaging system block diagram as shown in FIG. 3. Multi-region imagingsystem 1200 includes an optics group 1210, which in turn includes aplano/aspheric element 1220(1) at the front of the imaging system, andfirst and second K5/F2 doublets 1230 and 1240, respectively.Plano/aspheric element 1220(1) may be formed of, for example,poly(methyl methacrylate) (“PMMA”). Plano/aspheric element 1220(1) hasan aspheric surface 1292(1), described below; related optical systemsutilizing a plano/plano element 1220(2) or modified plano/asphericelements 1220(3) or 1220(4) in place of element 1220(1) are alsodescribed further below. Optics group 1210 is configured to directincident rays 1250 toward a sensor 1260. Sensor 1260 may be, but notlimited to, a complementary metal oxide semiconductor (“CMOS”) sensorconfigured for receiving a portion 1265 of incident rays 1250, and forgenerating image data 1270 (represented by a dark arrow) in responsethereto. Image data 1270 may then be received at a processor 1280 forimage processing to form, for instance, a human-viewable image and/or aprocessing result for a task, such as bar code reading. The imageprocessing may utilize information of optics group 1210 to form thehuman-viewable image and/or the processing result so as to form imagesthat are sharp and clear in best focus regions of a scene imagedthereby, as discussed below.

TABLE 1 Surface Type Radius Thickness Glass Diameter Conic ObjectStandard Infinity Infinity 0 0 1291 Standard Infinity 0.3804 PMMA1.347194 0 1292(1)/Stop Evenasph Infinity 0.007652431 1.347194 0 1293Standard 3.285444 0.8864066 K5 2.48704 0 1294 Standard −2.3543980.2933432 F2 2.48704 0 1295 Standard −28.18008 2.168189 2.48704 0 1296Standard 2.883053 0.8417674 K5 2.104418 0 1297 Standard −1.5081670.242327 F2 2.104418 0 1298 Standard −5.335657 1.551752 2.104418 0 ImageStandard Infinity 0.0004286271 0

An exemplary prescription for the various optical surfaces formulti-region imaging system 1200 of FIG. 12 is summarized in TABLE 1,with the different surfaces (i.e., surfaces 1291 through 1298) aslabeled in FIG. 12. A radius of curvature value of “infinity”corresponds to a plano surface. Prescription details related toplano/aspheric element 1220 are further discussed immediatelyhereinafter in the following two examples.

When the multi-region imaging system described in reference to FIG. 12and TABLE 1 is modified by replacing plano/aspheric element 1220(1) witha plano/plano element 1220(2) (e.g., element 1220(2) has a secondsurface 1292(2) with no curvature) providing no phase modulation, thenoptics group 1210 produces a through-focus MTF curve 1300 at a spatialfrequency of 100 line pairs per millimeter (“lp/mm”), as shown in FIG.13. The resulting imaging system is essentially a traditional imagingsystem without phase modification or multi-region imagingcharacteristics. As expected, through-focus MTF curve 1300 exhibits asingle best focus peak 1310 with a peak height of approximately 0.8 innormalized units and a narrow peak width 1320 (indicated by adouble-headed arrow) and, consequently, a narrow depth of focus.

TABLE 2 SURFACE 1292(1) EVENASPH Coefficient on r2 0 Coefficient on r40.012940072 Coefficient on r6 0.33257242 Coefficient on r8 −1.4950249Coefficient on r10 −0.26830899 Coefficient on r12 8.0415913 Coefficienton r14 −8.6162206

FIG. 14 shows an exemplary aspheric surface 1400 suitable for use assurface 1292(1) of plano/aspheric element 1220(1) in multi-regionimaging system 1200 of FIG. 12. Aspheric coefficients corresponding toaspheric surface 1400 are summarized in TABLE 2. With the inclusion ofaspheric surface 1400 as surface 1292(1) in optics group 1210, athrough-focus MTF curve 1500, as shown in FIG. 15, results at a spatialfrequency of 100 lp/mm. Through-focus MTF curve 1500 includes first andsecond best focus regions 1510 and 1515, respectively, and a “don'tcare” region 1540, that is, through-focus MTF curve 1500 indicates thatthere is more than one region of focus shifts that correspond to bestfocus (two regions, in this example). It is understood that each regionof best focus corresponds to an object distance range, that is, a rangeof distance of an object from the multi-region imaging system (e.g.,distances of objects 330 and 335 from multi-region optics 310, FIG. 3).All of regions 1510, 1515 and 1540 are indicated by double headed arrowswithin dashed vertical lines, although it will be appreciated that theboundaries of each region may not be sharply defined. In FIG. 14, sincethey are separated by region 1540, regions 1510 and 1515 correspond toobject distance ranges that are discontiguous. In relation to theexample shown in FIG. 1, first best focus region 1510 may correspond tonear field imaging of, for example, barcode 30 or a business card (e.g.,a conjugate distance of ˜13 to 18 cm), while second best focus region1515 may correspond to far field imaging used for human viewed portraitimaging (e.g., a conjugate distance of ˜60 cm or greater, such that bestfocus regions 1510 and 1515 are separated by 40 cm or more). The peakheights of through-focus MTF curve 1500 in first and second best focusregions 1510 and 1515 are both approximately 0.27 in this example,although the peak heights may be adjusted through modification ofsurface 1292(1), according to the specific application. While thethrough-focus MTF values in “don't care” region 1540 do not need to below, the reduced through-focus MTF values in “don't care” regioncontributes to increased through-focus MTF values in first and secondbest focus regions 1510 and 1515, respectively, due to the principle ofconservation of ambiguity. Also, although the shapes of first and secondpeaks 1510 and 1515, respectively, are shown as being similar, the peakheights and widths of the first and second peaks may be tailored to meetthe specific needs of a given application.

FIGS. 16-19 show diffraction MTF curves for polychromatic (e.g., white)light for optics group 1210 in multi-region imaging system 1200 of FIG.12, including aspheric surface 1400 of FIG. 14 as surface 1292(1), atdifferent conjugate distances. FIG. 16 shows an MTF curve 1600 for aconjugate distance of infinity, and FIG. 17 shows an MTF curve 1700 fora conjugate distance of 60 cm. It may be noted that the values of MTFcurves 1600 and 1700 are quite high through the range of spatialfrequencies shown in FIGS. 16 and 17, thereby indicating thatmulti-region imaging system 1200 exhibits a high MTF value throughoutthe far field imaging region at conjugate distances of 60 cm or greater(e.g., corresponding to region 1515, FIG. 15). FIG. 18 shows an MTFcurve 1800 for a conjugate distance of 25 cm (i.e., in “don't care”region 1540, FIG. 15, between near field and far field); it may be seenthat MTF curve 1800 drops off quickly for spatial frequencies above ˜30or 40 cycles per millimeter, thereby indicating poor image quality inthis “don't care” region. Finally, FIG. 19 shows an MTF curve 1900 for aconjugate distance of 15 cm (e.g., corresponding to region 1510, FIG.15), which is suitable for near field imaging application such asbarcode imaging and business card reading. As may be seen in FIG. 19,MTF curve 1900 exhibits relatively high MTF values (e.g., ˜0.2 andhigher) throughout the spatial frequency region of interest, therebyindicating good imaging performance even at this near field conjugatedistance for the multi-region imaging system including optics group1210.

TABLE 3 Surface Type Radius Thickness Glass Diameter Conic ObjectStandard Infinity Infinity 0 0 1291 Standard Infinity 0.3804 PMMA1.347194 0 1292/Stop Evenasph Infinity 0.07652431 1.347194 0 1293Standard 3.285444 0.8864066 K5 2.48704 0 1294 Standard −2.3543980.2933432 F2 2.48704 0 1295 Standard −28.18008 2.168189 2.48704 0 1296Standard 2.883053 0.8417674 K5 2.104418 0 1297 Standard −1.5081670.242327 F2 2.104418 0 1298 Standard −5.335657 1.487967 2.104418 0 ImageStandard Infinity 0.05080852 0

TABLE 4 SURFACE 1292(3) EVENASPH Coefficient on r2 0 Coefficient on r4−0.03062278 Coefficient on r6 0.0042801507 Coefficient on r8 0.043959156Coefficient on r10 0.10487482 Coefficient on r12 −0.073525074Coefficient on r14 −0.32282005

FIG. 20 shows a through-focus MTF curve 2000, at a spatial frequency of100 lp/mm, for an alternative imaging system that has been optimized toprovide better imaging performance at 25 cm conjugate distance comparedto that of the multi-region imaging system whose through-focus MTF curveis shown in FIG. 15. That is, the alternative imaging system essentiallyincludes the components of multi-region imaging system 1200 of FIG. 12but with a prescription that is summarized in TABLES 3 and 4. Thealternative imaging system includes a plano/aspheric element 1220(3),having a second surface 1292(3) with aspheric coefficients summarized inTABLE 4, to provide better imaging performance at 25 cm conjugatedistance. It may be noted that through-focus MTF curve 2000 for thealternative multi-region imaging system includes multiple, wide humpsrather than a single narrow peak or two distinct peaks as in thepreviously discussed embodiments. Further differences in systemperformance may be seen by comparing the polychromatic diffraction MTFcurves shown in FIGS. 21-24, for the alternative multi-region imagingsystem, with those shown in FIGS. 16-19, corresponding to theperformance of optics group 1210 of multi-region imaging system 1200including aspheric surface 1400 as surface 1292(1). FIG. 21 shows an MTFcurve 2100 for a conjugate distance of infinity, FIG. 22 shows an MTFcurve 2200 for a conjugate distance of 60 cm, FIG. 23 shows an MTF curve2300 for a conjugate distance of 25 cm, and FIG. 24 shows an MTF curve2400 for a conjugate distance of 15 cm. In comparing FIGS. 21-24 withearlier described FIGS. 16-19, it may be seen that the MTF curves forthe alternative imaging system, while providing slightly betterperformance at 25 cm, are generally lower across the portrait and barcode regions.

TABLE 5 SURFACE 1292(4) CUSPLINE Zat 1/8 of S-D −0.0010485351 Zat 2/8 ofS-D −0.0010594568 Zat 3/8 of S-D −0.00082374686 Zat 4/8 of S-D−0.00057644724 Zat 5/8 of S-D 0 Zat 6/8 of S-D 0 Zat 7/8 of S-D 0 Zat8/8 of S-D 0

FIG. 25 illustrates another example of an aspheric surface 2500 suitablefor use as surface 1292(4) of plano/aspheric element 1220(4) ofmulti-region imaging system 1200 as shown in FIG. 12. Aspheric termsdescribing aspheric surface 2500 are summarized in TABLE 5, where thevariables are areas of zone and surface forms within each zone; that is,“Z” is the surface height, “S-D” stands for “surface diameter”, and“CUSPLINE” stands for cubic spline. Aspheric surface 2500 may begenerally described as a cubic spline over eight regions (dividedradially) of an aperture of plano/aspheric element 1220(4). It may beseen that approximately half of aspheric surface 2500 near an outerradius is purposely set to provide zero phase; that is, no new phase isadded by Plano/aspheric element 1220(4) in approximately one half of theradius of aspheric surface 2500. In contrast to aspheric surface 1400 ofFIG. 14, which is configured for providing a phase modification acrossan aperture of aspheric surface 1400, aspheric surface 2500 is insteadconfigured to provide a phase contour in a center portion.

FIG. 26 shows a through-focus MTF curve 2600 for optics group 1210modified with aspheric surface 2500 implemented as surface 1292(4) ofplano/aspheric element 1220. Through-focus MTF curve 2600 shows thatthis system performs as a multi-region imaging system by exhibitingfirst and second peaks 2610 and 2620, respectively, thereby indicatingthe system provides good imaging performance for two discontiguousobject distance ranges. It may be noted that, while aspheric surfaces1400 and 2500 of FIGS. 14 and 25, respectively, appear to be verydifferent in shape, the resulting through-focus MTF curves (as shown inFIGS. 15 and 26) are quite similar.

FIGS. 27-30 show polychromatic MTF curves for the same multi-regionimaging system whose through-focus performance is shown in FIG. 26. FIG.27 shows an MTF curve 2700 for a conjugate distance of infinity, FIG. 28shows an MTF curve 2800 for a conjugate distance of 60 cm, FIG. 29 showsan MTF curve 2900 for a conjugate distance of 25 cm, and FIG. 30 showsan MTF curve 3000 for a conjugate distance of 16 cm. The MTF curves arehigh at infinity and 60 cm (e.g., as shown in FIGS. 27 and 28) as wellas at 16 cm (e.g., as shown in FIG. 30). The MTF curve is low at 25 cm,FIG. 29. Again, such a multi-region imaging system may perform well inapplications like those described in conjunction with FIGS. 1 and 2.

TABLE 6 Thick- Surface Type Radius ness Glass Diameter Conic ObjectStandard Infinity Infinity 0 0 3191/ Evenasph −3.248996 1.26 Acrylic 1.40 Stop 3192 Evenasph −1.816729 0.59 2.1 0 3193 Evenasph 17.63372 1.36Acrylic 2.28 0 3194 Evenasph 4.099447 0.45 2.62 0 3195 Standard 2.5267971.49 Acrylic 2.28 0 3196 Standard 1.501278 1.097 1.6 0 3197 StandardInfinity 0.56 AF45 1.4768 0 3198 Standard Infinity 0.444 1.4768 0 ImageStandard Infinity 0.01971329 0

TABLE 5 EVENASPH SURFACE 3191 Coefficient on r2 −0.10705732 Coefficienton r4 −0.056828607 Coefficient on r6 0.01926084 Coefficient on r8−0.0082999141 SURFACE 3192 Coefficient on r2 −0.091811456 Coefficient onr4 0.037117963 SURFACE 3193 Coefficient on r2 −0.11868423 Coefficient onr4 0.53930859 Coefficient on r6 −0.010193681 SURFACE 3194 Coefficient onr2 −0.27850876

FIG. 31 shows another embodiment of a multi-region imaging system 3100.Multi-region imaging system 3100 is different from multi-region imagingsystem 1200 system of FIG. 12 in a number of ways. First, plano/asphericelement 1220 is not present in optics group 3110 of multi-region imagingsystem 3100. Instead, optics group 3110 includes first, second, thirdand fourth optical elements 3120, 3130, 3140 and 3150, respectively.Optical prescriptions describing surfaces 3191 through 3198 of opticsgroup 3110 are summarized in TABLES 6 and 7.

While the configuration of multi-region imaging system 1200 implementedan exit pupil phase function designed for specific performance at asingle wavelength (e.g., a “monochromatic exit pupil”) to achieve themulti-region imaging effect, multi-region imaging system 3100 isconfigured to implement an exit pupil phase function that achievesmulti-region imaging effects in the polychromatic through-focus MTFperformance of this system (e.g., a “polychromatic exit pupil”), asshown in FIG. 32. Like through-focus MTF curves 1500 of FIGS. 15 and2600 of FIG. 26, a through-focus MTF curve 3200 resulting from opticsgroup 3110 features distinct, first and second peaks 3210 and 3220,respectively, that correspond to discontiguous object distance ranges.

Monochromatic through-focus MTF curves that contribute to polychromaticthrough-focus MTF curve 3200 are shown in FIGS. 33-35, shown here tofurther illustrate the operation of multi-region imaging system 3000. Amonochromatic through-focus MTF curve 3300 for blue illumination isshown in FIG. 33. A monochromatic through-focus MTF curve 3400 for greenillumination is shown in FIG. 34. Finally, a monochromatic through-focusMTF curve 3500 for red illumination is shown in FIG. 35. Monochromaticthrough-focus MTF curves 3300, 3400 and 3500 for blue, green and redilluminations are very similar in shape, with the position of the peaksbeing shifted according to wavelength. However, while each of themonochromatic through-focus MTF curves of FIGS. 33-35 exhibits only asingle region of best focus, polychromatic through-focus MTF curve 3200,which represents a combination of all monochromatic through-focus MTFcurves, illustrates that multi-region imaging system 3100 does indeeddemonstrate multi-region imaging characteristics.

Polychromatic MTF curves for multi-region imaging system 3100 are shownin FIGS. 36-39 for different conjugate distances. FIG. 36 shows apolychromatic MTF curve 3600 for a conjugate distance of infinity, FIG.37 shows a polychromatic MTF curve 3700 for a conjugate distance of 60cm, FIG. 38 shows a polychromatic MTF curve 3800 for a conjugatedistance of 25 cm, and FIG. 39 shows a polychromatic MTF curve 3900 fora conjugate distance of 15 cm. It may be seen that the MTF curves atinfinity and 60 cm are high (i.e., as shown by polychromatic MTF curves3600 and 3700) as is the MTF curve at 15 cm (i.e., polychromatic MTFcurve 3900). The MTF at 25 cm is low (i.e., polychromatic MTF curve3800), which is fine since this conjugate distance falls in the “don'tcare” region. These polychromatic MTF curves over object distance aresimilar to those corresponding to multi-region imaging systems includingaspheric surfaces shown in FIGS. 14 and 25, although the system of FIG.30 is designed in a completely different method; that is, manipulationof a polychromatic exit pupil is an alternative method that may be usedin designing multi-region imaging systems.

Yet another method of realizing a multi-region imaging system is byincorporating sub-wavelength features into the imaging system. Suitablesub-wavelength features may be in the form of, for instance, diffractivefeatures, refractive index variations within a material, ormetamaterials. Such sub-wavelength features may be placed on a surfaceof an element in the optics group of, for example, multi-region imagingsystem 1200 or multi-region imaging system 3100. Sub-wavelength featuresmay also be implemented not as surface features but as refractive indexvariation in non-homogenous, volumetric optical designs. Whenimplemented as refractive index variation, stray light issues in highintensity illumination environments may be considerably reduced comparedto those present when using sub-wavelength surface features.

FIG. 40 shows a block diagram of an exemplary multi-region imagingsystem 4000 including sub-wavelength features. Multi-region imagingsystem 4000 includes an optics group 4010, which in turn includessub-wavelength feature optics 4012 and, optionally, additional imagingoptics 4014. In practice, sub-wavelength feature optics 4012 and imagingoptics 4014 may be combined, for example, into a monolithic and/orvolumetric non-homogenous optical structure.

FIG. 41 shows an exemplary sub-wavelength feature profile 4100 for phaseheight from 0 to λ/2. The vertical axis represents phase in units ofradians, while the horizontal axis represents distance across anaperture of sub-wavelength feature optics 4012. Such a profile may beused to modulate the exit pupil of the imaging system in order toachieve multi-region imaging characteristics. In the exemplary profileshown in FIG. 41, the largest phase in radians is on the order of π,which is equivalent to λ/2 where λ is a central illumination wavelength.Sub-wavelength feature profile 4100 is substantially equivalent to alens focusing surface modulo λ/2. The power of the lens may then be usedas a design variable. The profile is then describable by the followingequation:phase(r)=mod(αr ²,π),  Eq. (9)

where r denotes radius across the aperture and α is another designvariable. The example shown in FIG. 41 has α=30 and r=linspace(−1, 1,501), where “linspace” is a function in MATLAB® for generatinglinearly-spaced vectors.

FIG. 42 shows an AF plot 4200 corresponding to the combination of adiffraction-limited imaging system and sub-wavelength feature profile4100 of FIG. 41. Multi-region imaging characteristics are clearlyindicated by two distinct dark regions in AF plot 4200; a first region4210 is manifest as a dark, horizontal streak, and a second region 4220is shown as a slanted streak at an angle with respect to first region4210. When AF plot 4200 is compared with AF plots 1000 and 1100 shown inFIGS. 10 and 11, respectively, it may be noted that first and secondregions 4210 and 4220 are narrow compared to the broad, dark regions ofAF plots 1000 and 1100. If a phase modifying element, such as aplano/aspheric element including one of aspheric surfaces 1400 and 2500,were incorporated into optics group 4010, then optics group 4010 may beconfigured to exhibit a similar increased depth of field as themulti-region imaging systems corresponding to AF plots 1000 and 1100. Ifoptics group 4010 were configured to provide increased depth of field,then first and second regions 4210 and 4220, respectively, of AF plot4200 for the resulting multi-region imaging system would be broader thanthose shown in FIG. 42.

TABLE 8 AsphereSag = 0 RD NR Amp C n Amp*OctSag 1 1 −1 × 10−3 0 0 termsα1 α2 α3 α4 α5 α6 −64.728151 −25.528684 838.61428 −901.60107 −545.50556−1625.1365 α7 α8 α9 α10 α11 α12 3287.9754 0 0 0 0 0 β1 β2 β3 β4 β5 β6 46 8 10 12 14 β7 β8 β9 β10 β11 β12 16 0 0 0 0 0

Multi-region exit pupils may be designed to be circularly symmetric,non-circularly symmetric or non-symmetric. A symmetric but not circulardesign, such as those described in the aforementioned PCT patentapplication serial number PCT/US07/69573, may also be used. An exampleof the use of such a surface is illustrated in FIGS. 43-48. TABLE 8shows various aspheric terms that define an exit pupil surface sag 4300,shown in FIG. 43. Surface sag 4300 may be incorporated in a multi-regionimaging system, such as that shown in FIG. 12 at surface 2. Apolychromatic through-focus MTF curve 4400 for a multi-region imagingsystem including surface sag 4300 is shown in FIG. 44. Likethrough-focus MTF curves (see FIG. 15) of the previously discussedmulti-region imaging system, MTF curve 4400 includes two peaks inregions 4410 and 4415, separated by a “don't care” region 4440.Polychromatic through-focus MTF curves at a variety of object distancesfor this system are shown in FIGS. 45-48. MTF curves 4500 and 4600(FIGS. 45 and 46) at infinity and 60 cm, respectively, are high as isMTF curve 4800 at 15 cm (FIG. 48). MTF curve 4700 at 25 cm shown in FIG.47 is low.

Yet another type of multi-region imaging system is a spatially varyingmulti-region imaging system, which involves the introduction of anoptical path length difference (“OPD”) into a portion of the aperture ofan imaging system. As an exemplary scenario for application of aspatially varying multi-region imaging system, FIG. 49 shows a scene4900 as seen from the inside of an automobile. It may be noted thatobjects far from the automobile, such as a street sign 4910, aregenerally in an upper region of scene 4900 as seen through a windshield4920 (represented by a rectangle surrounding a portion of scene 4900)and over a car hood 4930.

One way to accurately image windshield 4920 itself as well as streetsign 4910 with a single imaging system in a single exposure is to use amulti-region imaging system. In such an automotive application, it maynot be necessary to clearly image windshield 4920 in its entirety; forexample, one portion of a suitable multi-region imaging system may beconfigured to image an upper region of scene 4900 for recognition of faraway objects, such as street sign 4910, while another portion isconfigured for imaging a small portion of windshield 4920 for detecting,for instance, dirt or rain on the windshield.

FIG. 50 shows a block diagram of an OPD-modifying imaging system 5000,in accordance with an embodiment, including OPD-modifying optics 5010(with optical axis 5015) for imaging a far object 5020, disposed farenough away from imaging optics 5010 such that it is effectively locatedat infinity, at a sensor 5030. OPD-modifying optics 5010 also image anear object 5040 at sensor 5030. In conventional imaging systems, if theimaging optics are first configured to focus at an object closer thaneffective infinity (e.g., near object 5040), any adjustment to re-focusthe imaging optics at an object at infinity always forces the movementof the imaging plane (and thus the sensor) farther away from the imagingoptics. OPD-modifying optics 5010, however, include an OPD-modifyingoptical configuration that allows OPD-modifying optics 5010 tosimultaneously focus far object 5020 at the same imaging plane as nearobject 40. That is, OPD-modifying optics 5010 requires the imaging plane(and thus sensor 5030) to move closer to optics 5010 to focus far object5020 on a portion of sensor 5030 while keeping near object 5040 in focusat the same imaging plane. Put another way, OPD-modifying optics 5010require a sensor translation that moves in the opposite direction, ascompared to a conventional design, to bring an infinity object to focus.An example of OPD-modifying imaging system 5000 is discussed in detailimmediately hereinafter.

TABLE 9 Surface Type Radius Thickness Glass Diameter Conic ObjectStandard Infinity Infinity 0 0 Stop Standard Infinity  0.0076524311.347194 0 5191 Standard 3.285444 0.8864066 K5 2.48704 0 5192 Standard−2.354398 02933432 F2 2.48704 0 5193 Standard −28.18008 2.168189 2.48704 0 5194 Standard 2.883053 0.8417674 K5 2.104418 0 5195 Standard−1.508167 0.242327  F2 2.104418 0 5196 Standard −5.335657 1.6077  2.104418 0 Image Standard Infinity 0.0004286271 0

FIG. 51 shows a block diagram of a spatially varying multi-regionimaging system 5100, in accordance with an embodiment. Multi-regionimaging system 5100 includes an aperture 5110 that limits rays 1250entering imaging optics 5120. Imaging optics 5120 include a firstdoublet 5125 (including surfaces 5191, 5192 and 5193) and a seconddoublet 5135 (including surfaces 5194, 5195 and 5196). Imaging optics5120 are configured for focusing light rays 5140 (encircled by a dashedoval) at a sensor 5150. TABLE 9 summarizes an exemplary opticalprescription of the various components of multi-region imaging system5100.

Still referring to FIG. 51, a portion 5160 (indicated by a dot-dashoval) of light rays 5140 traverses an OPD-modifying element 5170 beforeportion 5160 is incident on sensor 5150. In effect, the spatiallyvarying characteristics of multi-region imaging system 5100 areimplemented by OPD-modifying element 5170, which intersects portion 5160of light rays 5140 such that OPD-modifying element 5170 affects only thespatial field points across an object imaged onto a bottom half 5175(indicated by a bracket) of sensor 5150. Sensor 5150 then converts lightrays 5140 received thereon into electronic data 5180 (represented by anarrow) directed to a processor 5190 for processing, such as productionof a human viewable image or generation of a task-based result.Processor 5190 may also utilize information of optics 5120 andOPD-modifying element 5170 to optimize processing such that imagesgenerated from each of the bottom and top halves of sensor 5150 areclear and sharp. Alternatively, processor 5190 may be configured toprocess information from bottom and top halves of sensor 5150differently, in order to perform two different tasks according toinformation received at the bottom and top halves of sensor 5150.

Continuing to refer to FIG. 51, in one embodiment, OPD-modifying element5170 may be a plane parallel plate that acts to increase the opticalpath difference for some field points, thereby effectively changing theregion of best focus for the affected field points. OPD-modifyingelement 5170 may be, for instance, a plano/plano BK7 optical element ofthickness 0.831 mm. OPD-modifying optical element 5170 may beadditionally configured, for example, to correct for aberrations and/orto control chief ray angles for certain light rays imaged at sensor5150. As another example, by adding optical power to OPD-modifyingelement 5170, the effective focal length and magnification of a part ofthe image at sensor 5150 may be modified simultaneously.

FIG. 52 shows a polychromatic diffraction MTF curve 5200 for bottom half5175 of multi-region imaging system 5100 for an object at infinity(e.g., a street sign as seen from inside an automobile) for a spatialfrequency of 100 lp/mm. Monochromatic diffraction MTF curves would looksimilar to polychromatic diffraction MTF curve 5200, becauseOPD-modifying element 5170 is assumed to be achromatic. Similarly, FIG.53 shows a polychromatic diffraction MTF curve 5300 for bottom half 5175of multi-region imaging system 5100 for an object at 5 cm (e.g., at anautomobile windshield) at a spatial frequency of 100 lp/mm. It may beseen that bottom half 5175 exhibits a broad MTF curve for the object atinfinity while providing only a narrow MTF peak for the object at 5 cm,thereby indicating that bottom half 5175 provides good imaging forobjects at infinity while being a poor imager of close objects. That is,for example, dirt or debris on the windshield should minimally affectthe imaging performance at infinity through bottom half 5175.

In contrast, FIGS. 54 and 55 show polychromatic diffraction MTF curves5400 and 5500, respectively, for a top portion (i.e., the portionunaffected by OPD-modifying element 5170) of multi-region imaging system5100 for objects located at infinity and at 5 cm, respectively, at aspatial frequency of 100 lp/mm. By comparing MTF curves 5200 and 5300with 5400 and 5500, respectively, it may be seen that the top portion ofmulti-region imaging system 5100 provides poor imaging performance forfar away objects while exhibiting good imaging characteristics for nearobjects. MTF curves at the top half of the image are very poor for anobject at infinity, and are ideal for the windshield location. In otherwords, the top portion of multi-region imaging system, withoutOPD-modifying element 5170, provides an image of the windshield withgood imaging quality.

FIG. 56 shows plots of two through focus MTF curves for differentportions of multi-region imaging system 5100 for a spatial frequency of100 lp/mm. A first through focus MTF curve 5610 corresponds to thethrough focus MTF performance obtained at sensor 5150 withouttransmission through OPD-modifying element 5170. That is, first throughfocus MTF curve 5610 corresponds to performance of a near-field image(e.g., a conjugate distance of 5 cm). A second through focus MTF curve5620 corresponds to the through focus MTF performance obtained at sensor5150 in bottom half 5175 (i.e., the infinity focused portion of theimage). A 0.25 mm focus bias has been introduced to improve clarity.

Multi-region imaging system 5100 may be implemented in a variety ofways. For example, OPD-modifying element 5170 may be implemented as anextra piece of transmissive material disposed directly on a cover glassof sensor 5150. Alternatively, OPD-modifying element 5170 may beconfigured from multiple pieces of glass of varying thickness with eachpiece covering a part of an active region of the sensor, therebyproviding spatially-varying imaging. As another example, OPD-modifyingelement 5170 may be attached to a sensor cover glass with, for instance,a polymer bonder directly onto the cover glass or with stand-off postsfor providing an air gap between OPD-modifying element 5170 and thesensor cover glass. In another embodiment, OPD-modifying element 5170may be formed of an aspheric shape. A molded aspheric element may befurther configured to correct, for instance, aberrations, chief rayangle and intersecting focal length. As yet another alternative,OPD-modifying element 5170 may be configured to have a uniform thicknessbut a refractive index profile that varies across an aperture of theelement. The effect provided by an OPD-modifying element may also bedistributed across multiple optical surfaces and/or cover glasses withinan optical prescription of optics 5120. As yet another alternative, anOPD-modifying element may be configured as a part of a spacer wafer in awafer-level optical system. Furthermore, the refractive index and thecoefficient of thermal expansion of an OPD-modifying element and a coverplate may be matched.

FIGS. 57-62 show various configurations of glass suitable for use asOPD-modifying element 5170 in relation to sensor 5150. In each of FIGS.57-62, sensor 5150 is shown to include a photosensitive region 5705(indicated by a dashed rectangle) partially obscured by a piece of glass(indicated by a shaded region); the glass takes on various shapes inFIGS. 57-62. In FIG. 57, a configuration 5710 includes a rectangularOPD-modifying element 5720 that covers a portion of photosensitiveregion 5705. As discussed earlier, rectangular OPD-modifying element5720 is configured to cooperate with imaging optics 5120 to provide goodimaging performance of far away objects but not near objects. Theportion of photosensitive region 5705 that is not covered by rectangularOPD-modifying element 5720 cooperates with imaging optics 5120 toprovide good imaging performance of near objects.

FIG. 58 shows another configuration 5810 of an OPD-modifying element5820 including a rectangular cut-out 5830 in the lower right handcorner. FIG. 59 shows still another configuration 5910 of anOPD-modifying element 5920 including a rectangular cut-out 5930 in alower, center portion. Another configuration 6010 shown in FIG. 60includes an OPD-modifying element 6020 with a rectangular cut-out 6030in the center of sensor 5150. Still another configuration 6110 of FIG.61 includes an OPD-modifying element 6120 with a semi-circular cut-out6130 in a lower, center portion. Alternatively, a configuration 6210 ofFIG. 62 includes an OPD-modifying element 6220 with a trapezoidalcut-out 6230 in a lower, center portion. The specific shape of cut-outs5830, 5930, 6030, 6130 and 6230 may be configured according to aparticular application, such as an amount of sensitivity required forimaging near objects. Additionally, a thickness and shape ofOPD-modifying elements 5720, 5820, 5920, 6020, 6120 and 6220 may bedesigned according to a desired amount of back focal distance and/oroptical track modification.

FIGS. 63-75 illustrate exemplary configurations of OPD-modifyingelements suitable for use in accordance with embodiments describedherein. FIG. 63 shows a configuration 6300 including a sensor coverglass 6305 with an OPD-modifying element 6320 disposed in direct contactthereon. OPD-modifying element 6320 may be, for example, a piece ofborosilicate glass with a thickness of ˜1.16 millimeters. As analternative, a configuration 6400 includes a standoff arrangement 6410introduced between sensor cover glass 6305 and OPD-modifying element6320 so as to provide an air gap 6440 therebetween. Air gap 6440 may be,for example, between 10 to 30% of a thickness of OPD-modifying element6320.

Continuing to refer to FIGS. 63 and 64, a vertical edge 6325 ofOPD-modifying element 6320 may be problematic in certain situations,such as under bright light conditions in which light scattering off ofvertical edge 6325 may generate undesirable stray light at the sensor.One way to mitigate such stray light is by providing a light blockingtreatment (e.g., black paint, a black material or black fabric) or alight scattering treatment (e.g., sanding) at vertical edge 6325.Alternatively, rather than using a single piece of thick glass as theOPD-modifying element, a plurality of thin pieces of glass may be usedas shown in FIG. 65. For example, the plurality of thin pieces of glassmay be bonded together with an index matching bonding material. Aconfiguration 6500 includes an OPD-modifying element 6520, which in turnis formed from a plurality of alternating pieces of large and small,thin layers of glass 6522 and 6524, respectively. By alternating largeand small glass pieces 6522 and 6524, the edge of OPD-modifying element6520 is configured to be jagged, thereby diffusing the reflection ofincident light therefrom. As illustrated in configuration 6600 of FIG.66, an OPD-modifying element 6520 may be separated from sensor coverglass 6305 by a standoff arrangement 6610.

Stray light may also be mitigated by using a slanted edge configuration.FIG. 67 shows a configuration 6700 with an OPD-modifying element 6720,including a slanted edge 6725, disposed directly on a sensor cover glass6305. FIG. 68 shows a configuration 6800, in which OPD-modifying element6720 is separated from sensor cover glass 6305 with a spacer arrangement6810. FIG. 69 shows an alternative configuration 6900 with anOPD-modifying element 6920, including a reduced vertical edge 6925 and aslanted cover 6930 over a portion of sensor cover glass 6305. Inconfiguration 6900, a reduction of the length of vertical edge 6925combined with slanted cover 6930 further reduce stray light at anoptical path length discontinuity across the sensor aperture. FIG. 70shows another configuration 7000, in which an OPD-modifying element 6920is separated from sensor cover glass 6305 by a spacer arrangement 7010.FIG. 71 shows another configuration 7100 in which an OPD-modifyingelement 7120 includes a smooth transition 7125 from a thick portion 7127to a thin portion 7130, thereby eliminating the sharp discontinuity inoptical path length and reducing stray light, where additionally thebest focus region will track variation in distance to a windshield(e.g., when utilized in camera 75, FIG. 2). FIG. 72 shows aconfiguration 7200, in which OPD-modifying element 7120 is separatedfrom sensor cover glass 6305 by a spacer arrangement 7210. FIG. 73 showsanother configuration 7300, which features an OPD-modifying element 7320with a rounded transition 7325 providing a smooth transition from athick portion 7327 to a thin portion 7330 across an aperture ofOPD-modifying element 7320. FIG. 74 shows a configuration 7400, in whichOPD-modifying element 7320 is separated from sensor cover glass 6305 bya spacer arrangement 7410. Finally, FIG. 75 shows a configuration 7500with an OPD-modifying element 7520 including a plurality of grooves 7530to act as “light traps” for reducing stray light. Grooves 7530 may beformed, for example, by attaching a plurality of thin wires 7540 alongone edge of OPD-modifying element 7520. Grooves 7530, and optionallythin wires 7540, may be painted black to further reduce unwanted lightreflection.

There are many design methods that may be used to achieve multi-regionimaging systems. Six examples were described. Aspects of each of theseexamples may be combined, by those skilled in the art of optical/digitalimaging systems, to form new systems within the scope hereof.

Some possible combinations of features for the multi-region imagingsystem are:

-   -   1. OPD-modifying optics+digital signal processing (“DSP”) for        two or more best focus imaging regions;    -   2. OPD-modifying optics+DSP for two or more best focus imaging        regions for human viewed systems;    -   3. OPD-modifying optics+DSP for task based imaging over two or        more best focus imaging regions;    -   4. OPD-modifying optics for forming two or more best focus        imaging regions where the through focus MTF related to at least        one region is broader, or has an extended depth of field, than        without the OPD-modifying optics;    -   5. OPD-modifying optics from 4 that include continuous phase        modifications;    -   6. OPD-modifying optics from 4 that include discontinuous phase        optics;    -   7. OPD-modifying optics from 4 that use specially designed        chromatic aberration;    -   8. OPD-modifying optics from 4 that use sub-wavelength phase        variations;    -   9. OPD-modifying optics+DSP for two or more best focus imaging        regions for mobile phone applications;    -   10. OPD-modifying optics+DSP for task based imaging over two or        more best focus imaging regions for automotive applications;    -   11. OPD-modifying optics from 4 that are illumination dependent.    -   12. OPD-modifying sensors (electronics+package+cover glass) for        multi-region imaging;    -   13. Use of 12 for automobile applications; and    -   14. OPD-modifying multi-region imaging where spatial changes in        focus at the image plane are realized.

The changes described above, and others, may be made in the imagingsystem described herein without departing from the scope hereof. Itshould thus be noted that the matter contained in the above descriptionor shown in the accompanying drawings should be interpreted asillustrative and not in a limiting sense. The following claims areintended to cover all generic and specific features described herein, aswell as all statements of the scope of the present method and system,which, as a matter of language, might be said to fall there between.

What is claimed is:
 1. A multi-region imaging system, comprising: asingle aperture that limits light rays entering the imaging system;OPD-modifying optics and a sensor array, the OPD-modifying opticsforming an optical image at the sensor array, the sensor arrayconverting the optical image to a data stream; and a digital signalprocessor for processing the data stream to generate a final image; theOPD-modifying optics providing a first region in the optical image thatis characterized by a first range of best focus and a second region inthe optical image that is characterized by a second range of best focus,the first range and the second range corresponding to object distanceranges that are discontiguous; wherein the OPD-modifying optics impart,on the light rays entering through the single aperture, a continuousphase modification to provide the first and second regions in theoptical image corresponding to object distance ranges that arediscontiguous; wherein the digital signal processor utilizes informationof the OPD-modifying optics to process portions of the data streamcorresponding to the first region differently from portions of thedatastream corresponding to the second region to generate the finalimage.
 2. The imaging system of claim 1, wherein the digital signalprocessor is further configured for generating the final image as one ofa human viewable image and a machine viewable image.
 3. The imagingsystem of claim 1, wherein the OPD-modifying optics comprise at leastone of a molded material, an optical element including subwavelengthphase modifying features and a material including refractive indexvariation therein.
 4. The imaging system of claim 1, wherein theOPD-modifying optics comprise at least one of an aspheric element and apower-providing optical element.
 5. In an imaging system includingimaging optics, a single aperture for limiting light rays entering theimaging optics, a sensor array, and a digital signal processor, animprovement comprising: an OPD-modifying element disposed within theimaging system and intersecting at least a portion of the light rays,such that the OPD-modifying element cooperates with the imaging opticsand the sensor array to form a first image portion and a second imageportion from the light rays, the first image portion being in focus overa first conjugate distance range and the second image portion being infocus over a second conjugate distance range, the two conjugate distanceranges being separated by at least 40 cm; wherein the OPD-modifyingelement imparts, on the light rays entering through the single aperture,a continuous phase modification to provide the first and secondconjugate distance ranges that are discontiguous; wherein the digitalsignal processor utilizes information of the OPD-modifying optics toprocess the first and second image portions differently to generate afinal image.
 6. In a method of imaging utilizing imaging optics, and asensor array, and a digital signal processor, an improvement comprising:configuring the imaging optics such that electromagnetic energytransmitted through a single aperture, subsequently through the imagingoptics and incident on the sensor array forms an image that is in focusover at least two conjugate distance ranges for two respective portionsof the image, the two conjugate distance ranges being separated by atleast 40 cm; wherein configuring comprises incorporating a phasemodifying element into the imaging optics to generate the two respectiveportions of the image; wherein the phase modifying element imparts acontinuous phase modification to generate the two respective portions ofthe image that are discontiguous; wherein the digital signal processorutilizes information of the phase modifying element to process the tworespective portions of the image differently to generate a final image.7. The method of claim 6, wherein incorporating the phase modifyingelement comprises integrating, into the imaging optics, at least one ofan aspheric element and a power-providing optical element.
 8. The methodof claim 6, wherein incorporating the phase modifying element comprisesintegrating, into the imaging optics, at least one of a molded material,an optical element including subwavelength phase modifying features anda material including refractive index variation therein.